Thirty-seven people were killed in overnight clashes between opposition tribesmen and security forces after a truce, that had ended four days of fighting in the Yemeni capital, collapsed, a medic said on Wednesday

Most of the dead were combatants, said the medic from Jumhuriya hospital.

Heavy fighting raged on in the capital Sanaa on Wednesday, according to an AFP correspondent.

Fighting between tribesmen loyal to Sheikh Sadiq al-Ahmar, who heads the powerful Hashid federation, and security forces loyal to embattled President Ali Abdullah Saleh broke out in the city on Tuesday, shattering a truce announced on Friday.

The defence ministry's 26 september.Net news website said that tribesmen had on Wednesday occupied a building near the Southwest side of the presidential palace, which is located in the South of Sanaa.

In the North of the city, street fighting took place throughout the night in Al-Hasaba area, where Ahmar’s house is located, according to residents.

“We heard the sound of ambulances evacuating the wounded throughout the night,” one resident of Al-Hasaba told AFP.

One veiled woman, who gave her name as Umm Ahmed, said as she fled with her five children from Al-Hasaba that she was returning to her village. The little group was carrying plastic bags filled with their clothes.

Witnesses said that reinforcements from the Republican Guards, an elite unit loyal to the President, had been sent to Al-Hasaba.

A fourth army brigade camp located near the state television and radio headquarters was targeted by rockets, as was the interior ministry headquarters, witnesses said.

26 september.Net, meanwhile, said that government forces “regained control of a number of public buildings,” without specifying which ones.

The website had said on Tuesday that Ahmar’s tribesmen had seised both the headquarters of the ruling General People's Congress and the main offices of the water utility.

Saleh's government had accused Ahmar’s fighters of breaking the truce, but sources close to Ahmar said Saleh’s forces were to blame as they had opened firing on the tribal leader's compound in the north of the city.

Ahmar announced on Friday that “there is a truce between us and Ali Abdullah Saleh” for mediation to take place. He was speaking at a funeral for 30 of his fighters killed in four days of clashes with Saleh’s forces in the capital last week.

But he added: “If the Saleh regime wants a peaceful revolution, we are ready for that. If he chooses war, we will fight him.”

In March, Ahmar pledged his support for protesters who have been demonstrating since January for the departure from office of Saleh, who has been in power since 1978.

On Wednesday fighting came a day after regime forces shot dead seven people demonstrating against Saleh in Taez, South of Sanaa, witnesses said, after 21 people were killed ending a four-month sit-in in a central square.

The shootings drew international condemnation.

“We condemn those indiscriminate attacks by the Yemeni security forces,” state department deputy spokesman Mark Toner said, referring in particular to violence in Taez.

European Union foreign policy chief Catherine Ashton also voiced shock at the use of live rounds against protesters in Taez in a crackdown that the UN human rights office said had already killed more than 50 people since on Sunday.

Thirteen Yemeni soldiers were killed by militants in south Yemen on Tuesday: eight died from clashes with suspected Al Qaeda fighters, and five in a car bomb that targeted a military convoy, medics and security officials said.